Evènements

Novembre 2017

Vendredi, 3 Novembre, 2017

11h - Site Sophia

Random Lasers and Random Fiber Lasers : Recent Advances and Multidisciplinary Applications

Random Lasers (RL) are a new kind of coherent photon sources which do not require mirrors to provide gain feedback. Instead, they exploit the scattering of a strongly scattering media. In this talk, I shall review the advances in the understanding of RL over the last 20 years, including RL in colloidal dye systems, random fiber lasers, plasmonically enhanced RL, multiphoton pumping and rare earth doped RL. Recent applications in sensing, nanothermometry and imaging for biodiagnostics will be highlighted. The more recent multidisciplinary applications using RL and RFL as platforms for observation of physical statistics phenomena such as Lévy-like behavior, photonic spin glass behavior and turbulence will also be discussed, with emphasis on recent results obtained in the Photonics and Biophotonics Laboratory, DF/UFPE.

Vendredi, 10 Novembre, 2017

Visite
Séminaire

11h- Site Valrose

Magnetic microparticles vibration at low frequency: a new approach in fighting cancer

In the field of biotechnology, magnetic nanoparticles are increasingly used for a variety of applications since they allow to exert forces and torques on biological species. Based on top-down approaches (deposition, etching, lift-off), several types of micro/nano particles were prepared for various purposes. They include synthetic antiferromagnetic particles, vortex microdisks [1], magnetite multidomain particles, magnetic nanoswimmers.  A first part of the work has aimed at controlling the agglomeration/dispersion of these particles [2]. To avoid the agglomeration of the particles in solution, these particles are designed to exhibit superparamagnetic-like response and must have a susceptibility below a certain critical threshold to avoid their mutual self-polarization. Thanks to their anisotropic properties, they offer new degrees of freedom in their manipulation when dispersed in solutions [3]. This allows designing ferrofluids with novel properties. In particular interesting optical properties can be obtained [4]. Concerning biomedical applications, a recent approach for cancer cells destruction was proposed, based on the triggering of cancer cell spontaneous death through the mechanical vibration of anisotropic magnetic nanoparticles attached to the cells membrane at low frequencies (20Hz). The induction of cancer cells death was demonstrated in earlier work on glioblastoma cancer cells [5] and in this study with NiFe vortex particles on renal human cancer cells [6]. These results open great perspectives for new cancer treatments with reduced side effects.

[1] Leulmi, S., et al, Appl.Phys.Lett. 13, (2013) 132412.
[2] Joisten, H., et alAppl.Phys.Lett. 97, (2010) 253112. 
[3] Courcier, T.,et al, Appl.Phys.Lett. 99 (2011) 093107.
[4] A. Truong, et al, Sc. Reports 6,  31634 (2016). 
[5] D.H. Kim, et al, Nat. Mater. 9, (2010) 165–71. 
[6]  Leulmi, S., et al., Nanoscale, 7, (2015) 15904.

 

Vendredi, 17 Novembre, 2017

11h - Site Valrose

Gravitational waves - Recent observations by Virgo and LIGO

The new generation of gravitational wave detectors (LIGO in the U.S. and Virgo in Europe) has now succeeded in receiving signals from coalescing binaries made of black holes and of neutron stars. This talk will begin with a review of the physical nature of gravitational waves, the principles of operation of interferometric detectors, and the extreme measurement challenges that have been overcome. Descriptions of various issues with the interferometric detectors will be given, with special emphasis on experimental topics that are of interest to Artemis and possibly INPHYNI as well.

Vendredi, 24 Novembre, 2017

Séminaire

11h - Site Valrose

Dynamics of complex interfaces: lubrification films and high-frequency deformation of colloidal monolayers

New experimental tools and theoretical concepts allow for the design of interfaces with a large degree of complexity exhibiting original dynamics and reviving the interest for the physics of interfaces. In this seminar, we show two examples of this complexity through droplet confinement and dynamics of colloidal monolayers.

In a first part, we are interested in the motion of droplets in a confined, micrometric geometry, by considering the lubrication film effect on droplet velocities. When capillary forces dominate, the lubrication film thickness evolves non-linearly with the capillary number due to the viscous dissipation between the meniscus and the wall. However, this film may become thin enough (tens of nanometres) that intermolecular forces come into play and affect classical scalings. We present our interferometric method which yield highly resolved topographies of the shape of the interface and allow us to bring new insights into droplet dynamics in microfluidics. We then discuss the characterization of two dynamical regimes as the capillary number (droplet velocity) increases : (i) at low capillary numbers, the film thickness is constant and set by the disjoining pressure, (ii) above a critical capillary number, the interface behaviour is well described by a viscous scenario considering the different sources of viscous dissipation. Finally, we briefly present a refined model to predict the droplet velocity.

In a second part, we focus on particle-coated bubbles subjected to ultrasonic driving. Exposing a particle-coated bubble to ultrasound waves enables us to achieve high-frequency compression-expansion of the monolayer in the range 10-100 kHz. Interestingly, we find that the periodic compression and expansion of the interface drives a qualitatively different dynamical evolution of the monolayer compared to what is commonly observed under shear deformation. In particular, we observe self-assembly of the particles into a network of strings. We ascribe the emergence of this microstructure to transient interparticle interactions occurring during dynamic deformation. A simple force balance on a sphere attached to the interface by capillary forces, and undergoing oscillations normal to the interface, reveals that the inertia of the particle is important for a micron-sized colloid on the very short timescale of our experiments. The motion of the particle normal to the interface causes a dynamic deformation of the interface leading to transient capillary interactions between the particles. Particle-based simulations confirm that the emergence of strings can only be explained by the coupling of this transient deformation with the equilibrium deformation that is initially present due to nanoscale undulations of the contact line. This work provides the first demonstration of unique dynamical phenomena upon extreme deformation of complex fluid interfaces, and lays the foundations for future studies of out-of-equilibrium behaviour of 2D soft matter.

 

Mardi, 28 Novembre, 2017

Soutenance

13h - Site Valrose

Towards quantum applications based on photonic entanglement

Le but de cette thèse est de développer des sources d’intrication photonique en vue d’applications en sciences information quantique. Dans ce contexte, nous présentons une source très performante et entièrement guidée permettant, au moyen d’une boucle de Sagnac, la génération d’états hyper-intriqués en polarisation et en énergie-temps. La configuration guidée rend le dispositif versatile, efficace et compatible avec une large bande spectrale, répondant ainsi au besoin des systèmes et réseaux de communication fibrés. À cette fin, nous avons distribué simultanément dans différents canaux télécoms des paires de photons hyper-intriqués au moyen de multiplexeurs en longueur d’onde à 5 canaux (DWDM), augmentant de fait le débit. La qualité de l’intrication est validée par la violation d’une inégalité de Bell étuendue à un espace de Hilbert à 16 dimensions. Afin de pouvoir interfacer des photons aux longueurs d’ondes des télécommunications avec les bandes d’absorption des mémoires quantiques situées dans le visible, nous avons également développé une interface cohérente en longueur d’ondes. Un nouveau dispositif de métrologie quantique permettant la mesure avec une précision inégalée des effets de la dispersion chromatique dans les fibres optiques standards est également proposé. Notre approche "quantique" améliore la précision par un facteur 2.6 par rapport aux méthodes de mesures conventionnelles. Dans ce même contexte, nous avons aussi implémenté un nouveau protocole de metrologie de la phase de deux photons en ne détectant uniquement qu’un seul photon. Cette réalisation ouvre la voie à des applications potentielles simples s’appuyant sur peu de ressources au niveau de la détection. Finalement, dans la perspectives de la miniaturisation de dispositifs quantiques, nous avons démontré un générateur d’intrication annoncée intégré sur puce qui trouve des applications en calcul et metrologie quantique.